Composting key to reducing landfill

It’s estimated that 45 percent of household waste in rubbish bins is food. Council-led kerbside food waste collection will stop it ending up in landfill. But collecting and processing food waste for alternate use is not as easy as it sounds, requiring standalone collection methods and specialist processing technology. What’s happening now and how can food waste collection and composting scale up to capture the best use of this waste stream.

Earlier this year, Auckland Council rolled out a kerbside food scraps collection service to 20,000 households in Papakura, the first step in a bold plan that will take the initiative region-wide in 2021. The development sprouts from growing public interest in reducing waste. A survey of households shows over 70 percent agreement with the introduction of a food scraps collection service to tackle the 90,000 tonnes of food-waste sent to landfill each year.

People love the idea of wasting less food and creating compost to nourish soil and food crops. Little wonder so many Kiwis compost food waste, with household sustainability surveys showing around two-thirds of New Zealand households taking organic matters into their own hands by composting garden waste and kitchen scraps at home. Ten percent of households also claim to have worm farm.

However, putting a meaningful dent into the volume of food scraps sent to landfill requires local council backing and deep-pocketed processors, as specialist skills and processing plants to deliver an end-to-end process (from source separation, collection, composting and end markets), don’t come cheap.

EnviroWaste collects green waste from our transfer stations in Auckland and Hamilton, residential kerbside food waste and inedible food from commercial customers, and takes it to our composting and vermiculture (worm farm) facility in Hampton Downs. We’re currently processing around 8,000 tonnes of organics a year, which is set to rise to over 20,000 tonnes. This sounds like a lot, but we’re still taking just a tiny bite from the banquet hall-sized opportunity to capture and convert food waste to high-value material. Even so, getting to this point represents a multi-million dollar investment in plant and equipment.

EnviroWaste’s composting facility uses German technology called GORE – a bunker system combining aerated floors and synthetic covers to create a moist, oxygen-rich environment where microbes thrive, converting waste to compost in a matter of weeks. By comparison, this process could take more than a year in a typical backyard compost pile and additionally, many home compost systems use an anaerobic process (i.e. without aeration) which generates greenhouse gases. Our GORE system controls odours and greenhouse gases, which condense on the underside of the covers and drop back into the pile, where bacteria continue to break them down. In-ground trenching captures leachate, preventing groundwater contamination.

Increasing composting capacity requires further investment, but private operators like EnviroWaste will remain reluctant to ramp things up without councils committing to the wider rollout of kerbside food scraps collection services.

Inevitably, city residents will have to shoulder some of the cost as councils plot their zero waste strategies and pilot new collection schemes to minimise landfill. In the meantime, councils are calling for an increase to the $10 waste disposal levy the government currently charges on every tonne of rubbish disposed of in landfills.

Raising the government-imposed charge is likely to increase dumping fees across the country. Even so, New Zealand applies one of the lowest levies in the world – Australia's waste levies are up to $133 per tonne, while UK charges $160.

The relatively small levy makes it harder for councils to fund new collection services. What’s more, New Zealand is endowed with sustainable energy sources, so there are few if any reasons to subsidise systems, such as landfill gas collection for electricity generation – something we do at our Hampton Downs site, to help offset new investment.

Still, the signs are good for food waste collection. Commenting on the early success of the kerbside food scraps collection service in Papakura, Auckland councillor Penny Hulse said recycling food scraps will significantly reduce Auckland household waste from 160kg to 110kg per person by 2021. She expects the service will keep 75,000 tonnes of food waste from landfill in its first year.

Community-driven waste management is key to New Zealand’s zero-waste future. However, it requires a collective strategy that unites central and local government approaches to significantly reducing waste in all classes.

On this front, the Local Government Waste Management Manifesto, authored by industry group WasteMINZ, outlines a way forward to address waste issues and pave the way for modern waste management initiatives.